In recent years, an endoscopic apparatus that can perform a treatment by observing an organ in a body cavity and/or by using a treatment instrument through a treatment instrument channel as required has been widely used as medical equipment. In industrial fields also, an industrial endoscope has been widely used for observing/examining a flaw or corrosion, for example, within a small-diameter tube of a boiler, a turbine, an engine, a chemical plant and so on.
An endoscopic apparatus mainly includes a light source device that irradiates illumination light, an insertion section to be inserted into a body cavity or a small-diameter tube, and an operation section that operates to bend the insertion section. Illumination light transmitting means and/or observation light transmitting means are provided in the part from the operation section to the insertion section. The illumination light transmitting means may be a light guide fiber bundle that transmits illumination light to the end of the insertion section. The observation light transmitting means may be an image guide that transmits light from a subject obtained by irradiating illumination light thereto. The operation section includes an eye piece section for observing, by unaided eyes, the light from a subject transmitted through the image guide, for example, and a connecting section to the light source device for inputting predetermined illumination light to the light guide, for example.
As disclosed in Japanese Unexamined Patent Application Publication No. 2005-103325, an electronic endoscopic apparatus has been developed and practically used that can display an electronic image of an observed part on a monitor, for example, by providing a solid-state image pickup device such as a CCD at the end of the insertion section or the image guide end of the operation section, forming an image from the light from the observed part due to the illumination light outputted from the light guide onto an image pickup surface by an objective optical system, converting the light to an electric signal, and performing signal processing on the electric signal.
Even in a case where an electronic endoscopic apparatus used as a medical machine has a failure or an abnormality during a medical treatment, obtaining and operating a minimum function for performing the medical treatment is required. For this reason, an electronic endoscopic apparatus has operation modes for operations for different processing details, such as an operation for performing a normal medical treatment and an operation for a case where a failure occurs within the apparatus. The operation mode can be switched in accordance with an external mode instruction or the state of the apparatus. Notably, providing multiple operation modes allows each operation mode to check the other operation modes. Thus, whether the operation mode to be switched will operate normally or not can be checked before the operation mode is switched, which can advantageously improve the safety level.
The control section of an electronic endoscopic apparatus includes circuits for controlling components of the apparatus in accordance with the set values, which are inputted in advance, or an external operation instruction. Since the circuit to be used differs according to the operation mode, the circuit to be used is switched when the operation mode is switched. In a conventional electronic endoscopic apparatus, as shown in FIG. 6, a CPU and a peripheral circuit required for an operation are prepared and implemented for each operation mode. FIG. 6 is a block diagram illustrating the configuration of the control section of a conventional electronic endoscopic apparatus. For example, two operation modes may be defined including a normal use mode, which is an operation mode for performing a normal medical treatment, and a safety mode, which is an operation mode in a case where some failure occurs within the apparatus. In this case, as shown in FIG. 6, the control section includes a CPU 100 and peripheral circuit 101 for use in the normal mode and a CPU 102 and peripheral circuit 103 for use in the safety mode.
In a case where the operation modes are implemented on one substrate in the electronic endoscopic apparatus, the multiple CPUs 100 and 102 and the peripheral circuits 101 and 103 must be implemented on the substrate, which may disadvantageously increases the area of the substrate. In addition, since the multiple operation modes are not implemented simultaneously, the CPU 102 and peripheral circuit 103 are not used when the normal use mode is implemented while the CPU 100 and peripheral circuit 101 are not used when the safety mode is implemented. For this reason, the usage efficiency may be disadvantageously decreased.
In order to solve the problems, a method may be considered that can decrease the size of the circuits and improve the usage efficiency of the circuits by parenthesizing a circuit that can be used in common to commonly use the circuit as a common circuit in both operation modes or increase the implementation density of the circuit. However, in a case where the circuit to be used in each operation mode and the common circuit are placed at remote positions from each other or the circuit to be used in the other operation mode must be separated, the signal path may be complicated. Then, even though the common circuit can be theoretically parenthesized, the implementation may be physically difficult, which is a problem. In addition, since a high implementation density of the circuit may not allow a sufficient clearance between signal lines or between circuits, the possibility increases that a short circuit may be established or an improper operation may occur due to the contact between the signal lines or parts, which may disadvantageously decrease the reliability.
Such an electronic endoscopic apparatus includes a controller for controlling components of the apparatus in accordance with set values, which are inputted in advance, or an external operation instruction. In a case where the controller includes a CPU (central processing unit), an FPGA (Field Programmable Gate Array) and a CPLD (Complex Programmable Logic Device), abnormality monitoring means is generally provided therein that includes runaway detection means for detecting their runaway and reset means for resetting the controller and initializing an operation if the state that the controller runs away is detected in order to prevent causing damage on the controlled machine from the operation of the runaway controller.
A watch dog timer is widely known and is generally used as the abnormality monitoring means. The watch dog timer is directly connected to a controller to be monitored and monitors pulse signals at predetermined intervals for clearing the timer implemented in software by the controller by controlling the output port in order to monitor whether the controller is operating normally or not. The watch dog timer then outputs a reset signal to the controller in a case where the controller has an abnormal operation state and cannot output a pulse signal and no pulse signals occur in a certain period of time. During the timeout period from the time when the timer is cleared to the time when the reset is outputted, each watch dog timer has an inherent value, and a watch dog timer suitable for the specifications of the controller must therefore be selected to use.
However, in a case where the controller of an electronic endoscope includes an FPGA and a CPLD, which internally includes a CPU, the initialization of software is not started until the configuration completes upon power-up of the apparatus. For this reason, it takes time to start up the CPU. In a case where a watch dog timer is selected that has a shorter time out period than the startup time of the CPU, the pulse signals at predetermined cycles for clearing the timer are not outputted during the startup of the CPU. Then, the reset is outputted during the startup of the CPU, and the apparatus may be repetitively restarted upon power-up.
In order to avoid the problem, a watch dog timer having a longer timeout period than the startup time of the CPU must be used. In this case, the repetitive restart can be prevented upon power up of the CPU, but the timing for starting the reset may be delayed in a case where the CPU runs away during diagnosis or observation. For example, in a case where the CPU runs away when the insertion section is in a body cavity, the apparatus may perform an improper operation that possibly hurts the body cavity. Therefore, there is a problem that it is difficult to use a watch dog timer having a longer timeout period for safety problem in a medical apparatus such as an electronic endoscope.
Accordingly, it is an object of the present invention to provide an electronic endoscopic apparatus that can improve the usage efficiency of the circuit of a control section and improve the reliability of operations of the circuit.
It is another object of the present invention to provide an electronic endoscopic apparatus that can prevent a CPU from repetitively restarting even when a watch dog timer having a shorter timeout period than the startup time of the CPU.